1. Technical Field
Several aspects of the present invention relates to a technology that controls various driven elements, such as an organic light emitting diode (hereinafter, referred to as “OLED”) element, a liquid crystal element, an electrophoretic element, an electrochromic element, an electron emission element and a resistance element.
2. Related Art
Various technologies have been proposed for driving various driven elements. Japanese Unexamined Patent Application Publication No. 2003-122301 (specifically, FIG. 1), for example, describes a configuration in which a plurality of unit circuits, each of which includes an OLED element as a driven element, are arranged in a planar manner. Each of the unit circuits includes a driving transistor, a reset transistor and a light emission control transistor. The driving transistor controls an electric current supplied to the OLED element in accordance with its gate voltage. The reset transistor connects the driving transistor to a diode. The light emission control transistor switches the supply/interrupt of electric current to the OLED element. According to the configuration described in JP-A-2003-122301, it is possible to compensate for an error (variation) of a threshold voltage of the driving transistor in each of the unit circuits.
In the meantime, the total number of transistors that form a single unit circuit is desirably small. As the number of transistors increases, the configuration of the unit circuit becomes complex. Thus, manufacturing costs increase. In addition, in an electro-optical device that uses unit circuits as pixels, there is a problem that, as the total number of transistors increases, the aperture ratio decreases. However, it is difficult to reduce the total number of transistors in each of the unit circuits. For example, in the configuration described in JP-A-2003-122301, in order to turn off the OLED element during a period when data are written to the corresponding unit circuit, it is impossible to omit a light emission control transistor.